Exploring the structure and mechanism of formation of an artificial protein capsid, toward the development of a novel redox-responsive nano-carrier system

2015 Fiscal Year Final Research Report

• Project/Area Number: 25560231
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Biomedical engineering/Biomaterial science and engineering
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Malay Ali 国立研究開発法人理化学研究所, 環境資源科学研究センター, 研究員 (40467006)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: protein cage / self-assembly / bionanotechnology / gold nanoparticle / metal coordination / artificial capsid / smart nanomaterial / supramolecular assembly

Outline of Final Research Achievements

We present a new method for assembling protein cages with well-defined, symmetrical structures. The starting material, a mutated TRAP protein, folds into an 11-membered ring with cysteine residues on the outer surface. Reaction with the gold cluster Au55 leads to the formation of a hollow cage (TRAP-cage), which exhibits extreme stability, yet disassembles under reducing conditions. Potential applications in biomedicine (drug delivery) are suggested.
The TRAP-cage structure yielded unexpected results. Neighboring TRAP rings were linked by gold atoms coordinated via cysteines: TRAP-cage represents the first de novo assembled protein cage by metal coordination. Furthermore, with 264 protein subunits, TRAP-cage shows a unique symmetry. Instead of icosahedral symmetry, TRAP-cage has snub cube symmetry, with an 11mer ring occupying each of the 24 vertices with near-perfect regularity. Our findings suggest novel strategies for building large protein cages by exploring alternative symmetries.

Free Research Field

生化学、バイオナノテクノロジー